Relay Cropping / Intercropping / Crop Rotation

A New Twist on Cropping - Living Legume Mulches (2008)

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Many producers are interested in sustainable crop production systems that reduce the application of chemical fertilizers and pesticides. Incorporating a 'living mulch' in cereal silage production might help achieve this for certain producers.

Living mulches are a form of intercropping. Intercropping is the cultivation of two or more plant species in the same field at the same time. A living mulch is an established legume cover crop into which an annual row crop is seeded. Often that annual row crop is a cereal, such as triticale or barley. Forage legumes are ideal for use as living mulches because they can be low growing and perennial. Using a perennial forage legume allows the living mulch to be maintained for multiple years without reseeding.

There are many benefits to using a legume living mulch. Forage legumes fix nitrogen through their relationship with soil microbes called rhizobia. If more nitrogen is fixed than the legume plant needs, this excess nitrogen may be released into the soil. Once in the soil, the nitrogen can then be taken up by the cereal crop. Decomposition of legume leaves and roots also adds nitrogen to the soil.

The ground cover provided by the legume living mulch helps control weeds through competition. For example, the legume living mulch can shade emerging weed seedlings, reducing their growth. The legume living mulch can also decrease cereal leaf disease incidence by acting as a barrier to pathogen spread between cereal plants.

The legume and cereal occupy different above and below-ground niches. They complement each other, increasing the cropping system's ability to capture and use resources, such as sunlight, water, and soil nutrients, efficiently.

The legume living mulch can increase the economic sustainability of a producer by decreasing the need for expensive inputs, such as nitrogen fertilizer and herbicides. It can also increase his environmental sustainability by providing constant ground cover to reduce wind and water erosion

Growing a cereal for silage in a forage legume living mulch would increase its forage quality. The protein-rich legume leaves would increase the crude protein content of the silage, while decreasing fibre levels.

Some suppression of the established living mulch in the spring before seeding your cereal is needed. This suppression could be a reduced herbicide application ten to 14 days before seeding or mowing the legume a couple days before.

What forage legume would be a good candidate for use as a living mulch? A fairly fast establishing, low growing legume would be ideal. If you are planning on maintaining the living mulch for multiple years, longevity and winter-hardiness would be two other characteristics to consider. Ultimately, the legume you choose will depend on the growing conditions in your area, and could vary from alsike to white to red clover for example.

One legume that has shown promise as a living mulch in Alberta is kura clover. Kura clover is relatively new to the province, and is currently used in the United States in mixed pastures. Kura clover living mulches have the potential to be adopted for barley or triticale silage production in Alberta, creating systems with lower input costs and increased forage quality.

For more information please contact
Stephanie Kosinski, Forage Specialist with Alberta Agriculture

Source: The Blade - Grey Wooded Forage Association, May 2008.

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A Receipe for Relay Cropping

By: Dr. Shabtai Bittman


Relay cropping entails growing 2 crops on the same piece of land (inter-cropping), at least for a part of the season. Intercropping is rarely practiced in industrial agriculture because of the difficulties involved in controlling weeds along with planting and harvesting the 2 crops. All these factors need to be considered to successfully relay-crop. Remember that corn is a heat loving plant and ryegrass grows best under cool moist conditions.

Planting corn

Plant corn early, late April to early May. This will allow you to harvest the corn early, one of the most important secrets of success. Early (low heat unit) corn hybrids will favor early harvest. If planting after mid-May, pay very close attention to heat-loving annual weeds (see weed control section, below).

Use normal corn populations of 75,000 plants per ha. The ryegrass will perform best where the corn is thin, but deliberately favoring the ryegrass by reducing corn density is not economical.

Planting ryegrass

Plant ryegrass when the corn has 3-6 leaves. Planting when the corn is smaller will enable the ryegrass to suppress corn yield. Planting after 6 leaves will produce thin spindly ryegrass plants.

Plant ryegrass at 25-30 kg/ha. Plant in strips between corn rows taking into account the weed control program (below).

Ryegrass varieties

One of our greatest break-throughs was discovering that only tetraploid, biennial Italian Ryegrass varieties are suitable for relay cropping. Annual and diploid varieties will not persist well in the corn understory. Our suspicion is that successful persistence depends on resistance to several diseases, in particular a fungus called Fusarium.

Check with your local seed supplier for the current list of available varieties.

Weed control

This is the big challenge. Italian Ryegrass will not persist in weedy corn fields.

In Canada, the best method to control weedy grasses, especially barnyard grass, is to apply Primextra (atrzine and metolachlor) prior to or just after seeding. Some incorporation of herbicides is necessary unless there is ample moisture. The herbicide will not allow the ryegrass to establish, so it must be applied in bands over the corn rows only. This is best done by spraying at seeding time, with the sprayer mounted on the planter. Weeds between rows can be cultivated. This can only be done prior to seeding. Cultivation should be shallow to prevent root pruning and to avoid drying out the soil prior to grass seeding.

Many broadleaf weeds are controlled by Primextra, but those that are not can be sprayed after corn emergence but prior to grass seeding with a number of registered products.

Harvesting the corn

It is very important to harvest the corn as early as possible. By harvesting 10-14 days earlier the fall growth of the ryegrass may be increased by over 30%.

Some tire traffic is inevitable but attention must be paid to drive over the corn rows as much as possible and avoid driving over the grass until it is well established.

Fertilizing in spring

For best spring yield and quality, apply 50-60kg N per ha as fertilizer or slurry manure in late winter or early spring.


Ryegrass is probably nearly as winter hardy as winter wheat but less hardy than fall rye. Very small plants are less hardy to low temperature, heaving and needle-ice than well-rooted plants. We have not lost ryegrass at Agassiz in the past 5 years.

Flooding tolerance

Small ryegrass plants will withstand some flooding, but ongoing flooding for more than 1-2 weeks will severely hamper the ryegrass.

Using the ryegreass

Italian Ryegrass is reputed to be the highest quality of cool season grasses. Ryegrass is very well suited to grazing, and cows can be put out early because of early growth. Damage to the stand or compaction of wet soil is of minor concern since the field will usually be prepared again for corn.

Ryegrass also makes good green-feed and silage, although it is difficult to cure.

Fall grazing would rarely be possible in Canada, but may be practical near the coast and in the US.

The relay crop can be left through the next summer to take advantage of its high quality. To succeed farmers should consider logistics.

Can you apply manure to a relay crop in the fall?

Research is underway to determine if some manure can be applied in the fall without fear of leaching.

Eliminating the stand in the spring

Roundup will not kill ryegrass in the spring. Ploughing and allowing some rotting of the sod is the best method. Intense grazing prior to ploughing will help break down the sod.

Effect on subsequent nutrient requirement of corn

Nutrient requirements for corn will increase following a relay crop, giving greater opportunity for use of slurry manure.

Does Relay Cropping Pay?

By Andrea Harris

We compared the economic viability of a elay cropping system to two alternative cropping scenarios:

1) Fall Rye Cover Crop

2) No Cover Crop

The returns and variable costs of the three cropping systems were compared using partial budgeting. Our analysis shows that, in addition to contributing to environmental sustainability, relay cropping provides a substantial contribution to net farm income relative to conventional cropping systems.

Table 1: Partial Budget Comparision of 3 Cover Cropping Scenarios.
Budget Items Fall Rye Cover Crop vs. no Cover

$ Change

Relay Crop vs. no cover

$ Change

Relay Crop vs. Fall Rye Cover

$ Change

Grass Forage $72 $130 $58
Variable Costs *
Seed $21 $24 $3
Fertilizer $0 $0 $0
Herbicide $0 -$26 -$26
Machinery op. $68 $77 $8
Custom Work -$10 -$17 -$7
Change in Net Farm Income** $7 $72 $79

In Table 1 the results from the corn-cropping model are presented by comparing the annual change in the returns and the variable costs associated with the three scenarios.

The benefits from relay cropping are substantially higher (10%) than those associated with either a straight corn (no cover) or a fall planted cover-cropping system. This is primarily the result of higher value grass forage and savings in fertilizer costs. The returns with a fall planted cover are slightly lower than those associated with a no cover system (-1%)

The estimated annual increase in farm income from relay cropping is $72 per acre, relative to a no cover system. An extra cost of $77 per acre, for machinery operation and $24 for seed is incurred. However, these costs are offset by the additional $130 return on grass forage, a savings of $26 on herbicides, and a savings of $17 in custom work. Relative to a fall planted covercropping system, relay cropping represents an increase in annual net income of $79. This is primarily due to a higher value forage crop and the savings realized by band spraying pre-emergent herbicides only on the corn rows, rather than the entire field.

Table 2: Effect of Growth Stage & Harvest Date on Yields and Benefits, based on 3 years of testing.
  Ryegrass Yield (t/ha) Corn Yield (t/ha) Benefits - Expenses
Growth Stage
3-leaf 1.2 28 $882
6-leaf 1.2 28 $927
9-leaf 1.0 29 $907
Harvest Date
09/7 1.6 25 $787
09/20 1.0 29 $910

An annual decrease of $7 per acre, or 1 percent, in net farm income is anticipated with the fall rye cover cropping system versus a conventional no cover system. The extra costs include $21 per acre for grass seed, $15 per acre custom manure spreading charge, and $68 per acre to undertake the extra field operations required for cover cropping. This increase in costs outweighs the additional $72 return on grass forage and the $25 savings in custom work.

The results from field and research trials have shown that there is no negative effect on corn yield when Italian ryegrass is planted between corn rows at the 3-6 leaf stage of corn growth. However, research on relay cropping undertaken by Agriculture and Agri-food Canada has indicated that grass and corn yields are affected by: a) the growth stage of corn at the time of grass planting; and b) the date of corn harvest. As a result of this research it was concluded that in order to maximize yields, the optimal time to plant Italian ryegrass as a relay crop is at the 6-leaf stage of corn growth.

Although a higher corn yield can be achieved at a later harvest date, a later harvest date will also result in lower grass yields. The first two columns in Table 2 summarize these results. The last column of Table 2 outlines the corresponding net crop related benefits as calculated in this study.

When combined, these results indicate that a later harvest date will result in greater increase in farm income and that planting ryegrass at the 6-leaf stage not only maximizes corn and grass yields, but also maximizes the net economic benefits from relay cropping.

Is Fusarium the Hidden Killer?

By Orlando Schmidt and Dr. Shabtai Bittman

In July of 1995, a tour group visited several farms that were experimenting with relay cropping for the first time. One of the stops was at the Hodgins-Smith Farm in yarrow. The group was immediately impressed with the uniform well-established grass crop growing between the corn rows. Ag-Canada researcher Shabtai Bittman exuberantly proclaimed "This is the winner!"

Less than 2 months later, the corn was off and the field was exposed. The results were less than impressive! A vehicle driving by would not have know a grass crop had been planted there. Why the dramatic change?

Certainly part of the problem was equipment related. Because of a high water table in the area, the soil was quite moist and harvest equipment left its share of ruts.

Upon a closer look, it was apparent that many plants that were thriving a few months earlier were now dead. Weed control on this field was excellent and soil moisture was adequate. This begs the question "Is fusarium the hidden killer?"

In his textbook Plant Pathology (1978), George Agrios describes fusarium as a Vascular Wilt, a family of widespread, very destructive fungal plant diseases. Symptoms are "More or less rapid wilting, browning, and dying of leaves and succulent shoots of plants followed by the final death of the plant." Entire death of plants can occur within weeks.

Fusarium lives in the soil and infects plants through the roots. Once in a field, fusarium is there forever. A wide variety of plants including annual vegetables, flowers, and weeds are known to be affected by fusarium.

In the field, the best control technique is planting resistant crop varieties. Unfortunately, not much is known about resistance to fusarium within the family of Tetraploid Italian Ryegrasses.

Is fusarium the hidden killer? Time will tell. Over the next few years, it will be important to continue monitoring relay-cropping fields with fusarium like symptoms. If plant samples are collected in the right time, diagnostic tests can be performed to confirm its presence or absence. In the meantime, it is recommended that growers use varieties, which have proven to be persistent within Ag-Canada's variety test program.

Multiple Benefits Make Relay Cropping a Good Option for Producers (2005)

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Multiple Benefits Make Relay Cropping a Good Option for Producers

Two crops are better than one, or at least that appears to be the case in ongoing relay cropping research at Agriculture and Agri-Food Canada's Pacific Agri-Food Research Centre (AAFC-PARC) in Agassiz, B.C.

"Italian ryegrass inter-seeded with corn in the spring is helping B.C. lower-mainland farmers use surplus soil nitrogen while producing excellent forage for livestock," says Dr. Shabtai Bittman, a forage and field crop management specialist at AAFC-PARC. The practice, known as relay cropping, further benefits the environment by significantly reducing the amount of nitrogen lost through leaching or to the atmosphere.

The research/extension project is being co-coordinated through the Pacific Field Corn Association and is supported in part with funds from the Greenhouse Gas Mitigation Program for Canadian Agriculture (GHGMP). A regional report about the research is available on the recently revamped Soil Conservation Council of Canada Web site at

The concept is to seed a second crop with corn that will continue to grow and use surplus nitrogen once corn has been harvested. In this case, Italian ryegrass emerged as the most suitable forage.

Surplus nitrogen in the usually heavy winter rainfall area of south-coast B.C. causes major environmental concerns because it can leach from soil and enter groundwater, says Sandra Traichel, of the Abbotsford Soil Conservation Association and a field co-coordinator for the GHGMP in B.C. Relay cropping is one possible way to reduce surplus nitrogen. Even with all the benefits, producer interest in relay cropping in Canada was slow in coming, says Bittman, but recent producer tours showing the success of the practice has generated considerable interest among B.C. producers in the past two years.

Italian ryegrass has proven to be a valuable forage for dairy cattle. A very palatable forage with good protein, the crop can yield three to five tonnes per hectare and can be used as silage, green feed and pasture.

"Relay cropping can play an important role in reducing the impact of surplus nitrogen on the environment," says Bittman. "And Italian ryegrass is not only an excellent forage, but can help producers reduce feeding costs."

The GHGMP supports a broad range of projects across Canada with the goal to promote awareness of agricultural practices that reduce greenhouse gas emissions. SCCC administers the delivery of the soil and nutrient management sector component of the program. For more information on activities, visit the SCCC's Web site at

For more information, contact::
Sandra Traichel
GHGMP field co-ordinater for southern B.C.
Phone: (604) 556-3732

Doug McKell, P. Ag.
Executive Director, SCCC
Phone: (306) 695-4212
Fax: (306) 695-4213
Web site:

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Relay Cropping Evaluated

By: Judy Walters Harvest is busy season for BC farmers. South-western BC dairy farmers are sometimes hard pressed to sow the cover crops they need to protect their soil from being eroded by heavy rains which characterize coastal winter weather.

Last fall, for example, some farmers' corn crops didn't mature until November. Other farmers who usually plant fall rye found that last fall's heavy rains made their field too wet to work.

The solution, says Orlando Schmidt, coordinator of the Dairy Producers Conservation Group (DPCG) is to plant a cover crop in the summer months.

Relay cropping is a new cropping system developed by Dr. Shabtai Bittman of Agriculture & Agri-Food Canada. It enables farmers to double crop their land, produce more home-grown forage, eliminate a time management bottleneck, and protect the environment by reducing soil erosion and impacts of manure and/or chemical fertilizer.

Italian ryegrass, a biennial grass, is used for relay cropping. Unlike fall rye, which must be sown after forage corn is harvested, Italian ryegrass can be sown into a standing crop.

 This relay-cropping field in Matsqui, shown in fall 1995 and spring 1996 yielded 6 t/ha dry matter. An economic study shows relay-cropping can increase returns by as much as $72 ($53U.S.) an acre.

"Italian ryegrass is sown between the rows of corn when the corn is at the 3-6 leaf stage, which is usually in late June" explains Schmidt.

Matsqui dairy farmer Bill Van Reeuwyk tried relay cropping last year. He drilled and broadcast Italian ryegrass on several small plots of land when his corn was 8 to 12 inches high.

Seeding a cover crop in the summer turned out to be a godsend for Van Reeuwyk, who milks 140 cows at Summershade Farms. "The harvest was late and the fall weather unseasonably wet. There's no way I would have had time to put in a crop of fall rye." The Italian ryegrass protected Van Reeuwyk's soil and gave him 50 extra acres of fall and spring pasture for his cattle.

Relay cropped Italian ryegrass not only alleviates the harvest-time crazies and yields additional feed, it protects the soil from erosion and improves nutrient uptake, says Saanich dairy farmer David Pendray, who also tried relay cropping last year.

Seed drills like this modified Vicon air-seeder are recommended as a preferred method of planting relay crops.

Soil and nutrient runoff management are "the most critical issues facing farmers today," says Pendray, who milks 225 cows with his brother Michael at Pendray Farms Ltd.

Tough new environmental regulations require farmers to ensure the manure they spread on their fields does not contaminate surface and ground water supplies.

If you sow Italian ryegrass in the summer, there's an established crop that can use the nitrogen you apply to your field, says Pendray. More important, the manure is available when the ryegrass needs it most.

Italian rylegrass is a superior quality feed, says Pendray. Compared to fall rye, Italian ryegrass is higher in nutrient quality and digestibility.

When Schmidt compared Italian ryegrass to fall rye he found the ryegrass had 15% protein, 25% acid detergent fibre, and 69% total digestible nutrients while the fall rye had 11.6% protein, 33% ADF and 63% TDN.

Italian ryegrass can either be left for pasture after the corn is harvested, cut and made into hay or silage, or ploughed under to improve the soil's structure and organic content.

Because relay cropping is new, there are still a few wrinkles to iron out. Weed problems, winter flooding, and extreme cold all pose a hazard to farmers. Most of the chemical controls that farmers would use to control weeds in their corn crop would kill their ryegrass, says Van Reeuwyk. "You can't sacrifice your corn crop for your ryegrass."

Inclement weather can prevent relay crops from getting properly established or surviving the winter.

 The Italian Ryegrass is shaded by the corn through the summer (left) slowing down the growth. Once the corn comes off though, the relay crop has a tremendous advantage over any fall planted cover crops (right).

Relay crops should only be sown in well-drained fields that have a history of few weed problems, recommends Schmidt.

Schmidt and agricultural economist Andrea Harris conducted an economic analysis of relay cropping with funding from the Canada-BC Farm Business Management Program. The CBCFBMP is a federal-provincial program designed to help farmers manage change, adopt modern farm business management principles and practices, improve their international competitiveness and self-reliance, address environmental issues, and ensure the long term sustainability of the industry.

The cost-benefit analysis of relay cropping shows that in addition to contributing to environmental sustainability, relay cropping provides a substantial contribution to net farm income relative to conventional cropping systems, says Schmidt.

Relay Cropping a Big Hit in Whatcom County

Is 'relay cropping' another example of Americans beating us at our own technology? Relay cropping is the system of planting Italian ryegrass into young corn stands (when the corn has 3-5 leaves) as a way to establish the ryegrass as a fall cover crop. After the corn is harvested, the ryegrass grows rapidly, protecting the soil and reducing leaching over winter, and producing high-quality feed in early spring. Although the system was developed at the AAFC Research Station at Agassiz, few BC farmers are using relay cropping. In contrast, over two-thirds of the corn fields across the border in Whatcom County are being relay-cropped. Whatcom farmers are benefiting from relaxed restrictions on fall manure applications on relay cropped fields and from a bonus of 3 t/ha (1.5T/acre) of high-quality feed in spring! So why not in BC?

When AAFC researchers first developed relay cropping, BC farmers did not have a registered herbicide to control grassy weeds, such as barnyardgrass, that was compatible with relay cropping. Agassiz researchers solved this problem by band spraying Primextra in 8cm (3in) bands over the corn rows at seeding. American farmers did not face this challenge. They could spray out barnyardgrass with the herbicide 'Frontier' before planting the ryegrass. With this in mind, custom worker Alan Yoder and friends, who had studied the research done at Agassiz, realized that relay cropping makes sense. His secret was developing an implement that cultivated, side-dressed and seeded the relay crop all in one pass. This year, Yoder and his associates relay-cropped about 2,500 ha (6,000 acres) of corn land in Whatcom County, where the concept has proven to be a winner for farmers, seed companies, the environment and custom workers.

Today farmers in BC can control grassy weeds in relay-cropped fields with the herbicide Accent. Will BC farmers choose to try relay cropping to see if they can also benefit from relaxed manure restrictions and a bonus crop?

O. Schmidt, BCMAFF, Abbotsford

Previous Page: « Corn - A New Pasture Grass? »

Relay Cropping for Forage Corn - A System in Demand!

The technique of relay cropping Italian ryegrass in forage corn was developed concurrently by Agriculture and Agri-Food Canada in the South Coastal Region of British Columbia and by government scientists in The Netherlands. It has become an important farming tool in several countries. Extension agents in Washington and Oregon have promoted this technology with great success, and it has also become an established practice with corn growers in the United Kingdom and The Netherlands.

Relay cropping is the technique of seeding a winter cover crop, often Italian ryegrass, into a young corn crop. The ryegrass germinates and grows slowly under the corn canopy. When the corn is harvested in the fall, the Italian ryegrass is already established and growth resumes, saving valuable time. Generally, the relay crop will have far more growth throughout the fall, winter and spring, than will any cover crop seeded in the fall. There are many advantages to relay cropping, with the main ones listed in box.

Is relay cropping being used in coastal BC where it was developed? Pendray Farms Ltd. is a 200-acre dairy farm on the Saanich Peninsula of Vancouver Island. Dave, John and Michael Pendray cooperated on some of the original large-plot trials testing relay cropping and have been using the technique ever since. The Pendrays have been relay cropping on all their corn land for the past three years. They plant Italian ryegrass into the corn using a small air seeder fitted with shoe-type openers spaced four inches apart. Seeding rate is usually around 28 kg/ha (25 lbs/acre). Time of planting is critical for successful establishment. If planted too early, the ryegrass may compete with the corn crop and if planted too late, establishment may be poor due to competition from the corn. The target time for planting should be when the corn is 15-20 cm (6 to 8 in.) tall. Pendrays indicate one drawback of this system is that ryegrass planting comes at a very busy time of year.

Weed control can be a challenge if weedy grasses have been a problem in the field. Pendrays have had reasonable success using Dual (metolachlor) plus atrazine applied as a pre-emergence band application over the corn row at planting. Cultivation, using a high speed Sukup cultivator, controls weeds in the inter-row space until time for ryegrass planting.

Advantages Of Relay Cropping
  • Greater fall and winter capture of nutrients remaining in the soil after corn harvest than with a conventionally planted cover crop.
  • May allow for environmentally sound application of more manure nutrients in the fall than is the case with fall-seeded cover crops.
  • Improved protection of soil from wind and water erosion and protection against raindrop impact.
  • Ensures cover crop establishment. Adverse fall weather conditions may mean you could not plant fall-seeded cover crops.
  • Improved support for harvesting equipment from the ryegrass sod when soil conditions are wet at harvest.
  • Production of more high-quality plant material for harvest or grazing in spring, or to return to the soil as green manure.
  • Reduces runoff in the winter. This means less sediment and fewer nutrients moving into surface water such as streams and ditches.

Dave Pendray says “In the spring of 1999, we planted Italian ryegrass into all our corn crop. This year we have one of the best relay crops ever. We have been very pleased with how this system saves us time in the fall, allows for earlier fall manure application and helps support heavy harvesting and manure application equipment. The added economic and environmental benefits are very important to us. Greater fall nutrient capture by the crop means reduced fertility costs for crops planted the following year. There are also major pluses from the environmental perspective due to prevention of nutrient and soil erosion losses.”

The benefits and success of relay cropping are well documented in the whole of the Pacific Northwest. With increased demands on farmers from both an economic and environmental perspective, this technique will be used on many more farms in the future.

Michael Betts, BCMAF, Sidney

Previous Page: « Grazing Corn in Winter »

Next Page: « Know How Much You Harvest... The Easy Weigh! »

Relay cropping produces top forage, benefits environment (2006)

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Fast growing grass provides ground cover and helps reduce surplus nitrogen.

Italian rye grass inter-seeded with corn in the spring is helping B.C. Lower Mainland farmers use surplus soil nitrogen and at the same time produce an excellent forage for livestock, says a Agriculture and Agri-Food Canada Researcher at Agassiz.

The practice, known as relay cropping, is beginning to catch on among dairy producers, says Dr. Shabtai Bittman, a forage and field crop management specialist at the Pacific Agri-Food Research Centre (PARC). "The Italian rye grass, over its growth cycle will remove about 100 kilograms of surplus nitrogen per hectare," says Bittman. "And it is one of the top forages to produce. It's a leading forage in New Zealand and Europe."

Relay cropping further benefits the environment by significantly reducing the amount of nitrogen lost through leaching and to the atmosphere. The research project, co-ordinated through the Pacific Field Corn Association, is supported in part with funds from the federal Greenhouse Gas Mitigation Program for Canadian Agriculture (GHGMP).

Forage seeded with corn

The concept is to seed a second crop with the corn that will continue to grow and use surplus nitrogen once the corn has been harvested, says Bittman. After looking at several options over the years, Italian rye grass emerged as one of the most suitable forages.

The Italian rye grass is inter-seeded when the silage corn is between the three to six leaf stage, which explains the term relay cropping. "It won't compete with the corn at that stage, and yet there is enough sunlight to allow the Italian rye grass to establish," he says. Growth of the rye grass is suspended once the corn crop canopy closes. But after the corn is harvested, in late September or early October, the rye grass begins growing again.

"It usually takes about 10 days after corn is harvested for the Italian rye grass to take off," says Bittman. "But it continues to grow into December." Bittman estimates the rye grass uses between 50 and 65 kilograms of nitrogen per hectare in fall. After resuming growth, usually in February, it will use another 40 to 50 kilograms of nitrogen before harvested as silage, greenfeed or used as pasture.

"The rye grass is not able to use all the surplus nitrogen in the soil, but it makes a significant difference," he says. "On average the crop removes about 100 kilograms of nitrogen per hectare whereas without it, surplus nitrogen use would be zero."

Environmental concerns

Surplus nitrogen in the usually heavy winter rainfall area of south-coastal B.C. causes major environmental concerns, points out Sandra Traichel, with the Abbotsford Soil Conservation Association and a field co-ordinator for the federal GHGMP in B.C.

Surplus nitrogen can be leached from soil and enter the groundwater, she says. And in waterlogged soil, it is also subject to a process of denitrification, which means the nitrogen is converted and released to the atmosphere as nitrous oxide, one of the more serious greenhouse gasses.

In two years of trials comparing application of manure on bare soil with manure application on grass fields, research showed a dramatic reduction in the production of nitrous oxide. "Vigorously growing grass really soaks up the nitrate," says Bittman. "We found a five to 10-fold reduction in nitrous oxide production on grassland compared to bare fields. It makes a significant difference."

To maximize the benefit of relay cropping it's important to use a forage with high feed value, says Bittman. Earlier research found fall rye also works as a relay crop, but it makes poor livestock feed. "Producers are inclined to plow it under rather than harvest the feed," he says. "And that practice just returns the nitrogen to the soil, so we don't really gain anything."

Excellent forage

But Italian rye grass has proven to be a valuable forage for dairy cattle. A very palatable forage with good protein, the crop can yield three to five tonnes per hectare and be used as silage, green feed and pasture.

Producer interest in relay cropping in Canada was slow in coming, says Bittman. Some U.S. Pacific Northwest producers saw relay cropping trials in B.C. and jumped on the practice much earlier. One reason is the U.S. producers had access to a herbicide which could effectively control barnyard grass that grew along with the Italian rye grass. Canada now has a registered herbicide to control the weed and not harm the forage.

A second reason for speedy U.S. adoption, was interest by at least one company to provide a custom service for inter-seeding the Italian rye grass into corn. "It made quite a difference for northern Washington and Oregon producers just to be able to hire someone to do the seeding," says Bittman. "Producers here are set up for row crops, but not all have access to grain seeding equipment."

Producer tours showing the success of relay cropping has generated considerable interest among B.C. producers. "One producer on southern Vancouver Island who has been relay cropping for several years is getting exceptional yields, and this year he had half his crop harvested by early April," says Bittman.

"It has proven to be an excellent forage," he adds. "And the grass crop plays an important role in reducing the impact of surplus nitrogen on the environment."


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Research Needs


On wet soils, tire tracks from harvesitng equipment will set back the relay crop. To avoid this problem, concentrate tire tracks over corn rows.

At least a dozen farms have tried relay cropping in South Coastal British Columbia since 1995. Why have some succeeded and others failed? This question teases the minds of researchers and farmers alike. Here are some research questions which still need attention.

  • Is the success of the relay crop related to the variety of corn crop planted? Some corn varieties have more of an upright leaf posture while others have more "floppy" leaves. An upright leaf posture allows more light through the canopy. We're not sure but we suspect varieties with upright leaves will work better in a relay-cropping scenario.
  • Why do some relay-cropped fields look so patchy after the corn comes off? We suspect that patchy relay crops are due to poor weed management, drought, disease, soil variation or a combination of these. Most likely, the reasons are different in each field. Further testing and observation is required to get a better handle on this question.
  • Can a relay crop survive in "40 ton/acre" corn? The higher the corn yield, the less light that is available for the relay crop. We have definitely observed that the ryegrass does not do as well in a bumper crop of corn. Further testing and fine-tuning is required to see if double-cropping can succeed in this environment.
  • Are there weed control products available for post-emergent control of grassy weeds? Part of the success with relay cropping in the U.S.A. is due to a wider range of herbicides to choose from. Agriculture & Agri-Food Canada is now conducting trials to attain minor use registration on a herbicide called Elim. If residual effects are not a problem, this product could provide a valuable tool for successful relay cropping.

Relay Cropping Reduces Runnoff

In a research trial conducted at the Pacific Agricultural Research Centre in Agassiz, Dr. Laurens Van Vliet compared rainfall runoff from a relay cropped corn system and a corn system without a cover crop.

Corn was planted in plots on a field with a gentle slope (5-10%). Runoff was collected and measured for each plot from May 1, 1996 to May 1, 1997. Table 3 shows the findings from this trial.

In a relay cropping system, the corn is harvested normally. The Italian Ryegrass may appear stressed at first but will quickly bounce back.

 In a relay cropping system, the corn is harvested normally. The Italian Ryegrass may appear stressed at first but will quickly bounce back.

Annual rainfall for this period was 1987mm, approximately 300 mm above average. The data, which represents the mean of 2 replicates, shows that runoff is reduced in the relay cropping plots by about 15%. It is quite likely that the difference in runoff is dramatically higher during storm events when runoff can be 50-60% of total rainfall and erosion potential is the greatest.

Although the data from Van Vliet is only from one calendar year, it shows that relay cropping has tremendous potential as an erosion control technique.

Rotation Benefits Organic and Conventional Farmers Alike (2008)

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Real estate people say that success is all about 'location, location, location'. Organic farming has a similar mantra and that is 'rotation, rotation, rotation'.

Disease, weed and insect cycles are a perpetual headache for any farmer and this is particularly true for the organic farmer. With limited inputs, the most important management tool is crop rotation. The plain truth is that a well-designed rotation not only makes organic farming possible, it can also work as an effective cost cutter for the conventional farmer.

This was the take home message recently delivered by John Hollinger, organic business development specialist for Manitoba Agriculture, Food and Rural Initiatives at the demonstration farm in Carman. It is her that a six year rotation designed by Dr. Margin Entz of the University of Manitoba has been running for the last four seasons.

"What we're trying to demonstrate is a practical crop rotation that organic farmers, or any farmers who are interested in sound agronomic practices, can use to produce a crop based on a 'stockless' regime," Hollinger explains. "If you don't have livestock but you have a rotation like this, it could very well work."

This 'stockless' approach is necessary for straight organic grain farms since they do not normally have access to manure that can be used as fertilizer. As a result, stockless organic farmers must find a different source of fertilizer for their land.

A three-pronged attack

A good rotation, whether it is organic or conventional, employs a three-pronged strategy with the first two prongs aimed at reducing the need for inputs. To begin with, rotations must first address the usual agricultural pests. To do this, a farmer has to anticipate the cycles of diseases and insects and use different crop types to break them up. It also has to include crops that can compete with weeds and, in an ideal system, reduce or even eliminate them.

The second part of the strategy deals with the health and fertility of the soil. A good rotation should help maintain high levels of both organic matter and the mirco-organisms that break it down into usable plant nutrients for the next crop generation. "a healthy soil grows healthy plants that can withstand stresses such as drought, bugs, or disease and can compete with weeds a lot better than plants that are not vigorous, Hollinger says.

The third prong is the economic prong, such as the saving of resources, the marketability of the crop and the resulting profitability of the farm. "So our six year rotation includes cereals, pulses and a green manure every three years." Hollinger says, "The green manure supplies enough nitrogen to replace what's being used up by the annual crops."

The green manure may be a legume, such as a clover, or in this case, hairy vetch. The vetch is a source of organic matter and a source of available nitrogen. "Hairy vetch is one of the best fixers of nitrogen out there and it provides very good competition for the weeds," Hollinger says. "The seed was bought in iowa for close to two dollars a pound Canadian and seeded at 20 pounds to the acres, so it's costing about $40 to seed the field, but you get at least 100 pounds of nitrogen fixed per acre."

After the vetch was worked in, they planted a cover crop of fall rye. Fall rye may seem an odd choice because there is not a very big organic market for it. However, fall rye exudes certain alkaloid compounds into the soil that inhibit weed germination, especially with small seeded annuals.

"When oats are used as a companion crop with the vetch, as we have in this demonstration, the oats may be used as a green feed or silage, so this crop would be swathed probably sometime in July just as the seeds are starting to fill," Hollinger says. "you'd get a lot of biomass for green feed or silage that can be sold to cattle farms, then the vetch continues developing and it can be worked into the ground in September."

On paper, the rotation starts with the green manure to get the soil nitrogen levels up. The next year, either an oilseed such as flax or some other broadleaf crop such as buckwheat is grown. The following year, spring wheat is grown.

Alternating the cereal and broadleaf crops break disease and bug cycles that may be developing. After another green manure year and another cereal crop, a pulse crop such as soybeans can be grown. A cover crop of fall rye after the soybean harvest may help to get row crop weeds under control before going back to a green manure at the start of another six year rotation.

"In 2006, the economics on this particular site showed up pretty well, including those lean years where you just have expenses and no income other than the contribution of nitrogen," Hollinger says. "If you figure with a green manure you're getting a hundred pounds of nitrogen then that's worth something, especially at today's prices of fertilizer."

Farmers wishing to try weed control and fertility through rotation should know that effective rotations are specific to their regions, so what works in Winkler, Manitoba, may not work in the Peace River region. Good record keeping is essential and a good working knowledge of the crop history, climate and soil geography of the farm is important.

Article by Gordon Leathers, Top Crop Manager (West) - January 2008

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